>Hi Ken,
> Thanks a lot for the reply. Can you please explain a little more about the
>two alternatives you have
>suggested for the simulation of differential pair? Can you please explain
>exactly how to

>(i)mock up differential pairs interactively in sigxp.

This all assumes you have 13-6 and the cadence default
libraries are loaded.

1) edit -> add part -> differential part

you should see the cadence default diff parts.
put those down and double click on CDSdefaultIO
replace the part with your own IO
set the parameters according to what your need (thresholds and stuff)
repeat as necessary depending on the number of different parts

If you need a '"packaged device" look at the IbisDevice diffpair that is in
the default
library

2) edit -> add part -> interconnect

I would chose the stripline-2 or microstrip-2 depending on requirements.
Those are
trace models, rather than lossless T-lines.

set parameters as needed. Look at the xsection information for the impedance,
velocity, diff-impedance ...

I would do it like that in order to ensure the coupling that you are design
for.

3) put down the topology

4) Double click on the wanted driver where it says tri-state enter the
wanted stimulus

5) hit the simulate button and all should be simulated with two drivers 180
phase
difference and the output combined.

>(ii)simulate differential pair at the board level.
>It would be nice if you can explain the method in terms of Specctraquest
>menus/commands.

IBIS dependent. If you go and set the diffpair pins in your IBIS model
it will be done for you automatically when you do a board level sim.

I don't do it pre-route. I am not sure what assumptions the pre-route
algorithm does based on the conductors that need to be next to
each other and obviously are not at that point.

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